Organic light emitting diode and method of manufacturing

ABSTRACT

Aspects of the present disclosure provide for manufacturing an organic light emitting diode (OLED) by forming two terminals of the OLED on two substrates of the display, and then depositing a plurality of layers of the OLED on one or both of the two terminals to form a first portion and a second portion of the OLED on each substrate. The two portions are joined together to form an assembled OLED. The deposition of the two portions can be stopped with each portion having approximately half of a common layer exposed. The two portions can then be aligned to be joined together and an annealing process can be employed to join together the two parts of the common layer and thereby form the OLED.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/514,886, filed Aug. 3, 2011, which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure generally relates to organic light emittingdiodes, particular to methods of manufacturing organic light emittingdiodes for use in displays such as active matrix organic light emittingdiode displays.

BACKGROUND

Displays can be created from an array of organic light emitting diodes(“OLEDs”) each controlled by individual circuits (i.e., pixel circuits).The individual circuits have transistors for selectively controlling thecircuits to be programmed with display information and to emit lightaccording to the display information. OLEDs are emissive display deviceswhich generally emit light according to the amount of current driventhrough the OLED. OLEDs generally include a light emitting region wherepositively charged holes meet with electrons. Light is emitted as theelectrons are captured by the holes and settle at a lower energy state.The amount of current driven through the OLED is thus proportionate tothe number of emission events, and the light emitted from an OLED isaccordingly related to the current driven through the OLED. Thin filmtransistors (“TFTs”) fabricated on a substrate can be incorporated intosuch displays to control the amount of current driven through the OLEDsaccording to the display information programmed into the individualcircuits.

OLEDs can be developed by sequentially depositing layers of materialonto a substrate. Such a layering process generally commences andterminates with depositing conductive electrodes (i.e., terminals) suchthat a completed OLED includes a plurality of layers disposed betweentwo electrodes. To connect the OLED to a TFT of a pixel circuit, anelectrical connection is generally made between a terminal of the TFTand one of the electrodes of the OLED through a contact, which processleads to problems due to the precision of the required alignment betweenthe contacts and the OLED terminal and the relative unreliability andinefficiency of the contacts formed.

Applying a voltage across the two electrodes in excess of an operatingvoltage associated with the OLED generally allows a current to flowthrough the device and for light to be emitted from an emission regionof the OLED. As the OLED ages, the operating voltage of the OLED canshift (e.g., increase). The shift in the OLED operating voltageinfluences the voltage applied across the TFT, and thereby modifies thecurrent flowing through the OLED, and thus influences the light outputof the OLED.

It is desirable, therefore, to configure the pixel circuit such that theterminal of the TFT coupled to the OLED does not influence the voltageapplied across the TFT. Such a structure is commonly referred to as areverse OLED, because one way to develop the structure is tosequentially develop the layers of the OLED in the reverse order. Oneway to develop a reverse OLED is to start the deposition on the displaysubstrate with the cathode terminal (“layer”) instead of the anodeterminal (“layer”). However, suitable transparent materials for use as acathode terminal with a suitably high work function are rare,unavailable and/or expensive. Furthermore, the performance of suchdevices as have been created is inferior to conventional OLED devices.

Another method for achieving the desired structure is to develop thenormal OLED on encapsulation glass and develop a matching contact on theTFT substrate. The two substrates can then be put together. However, thecontact quality between the OLED and the matching contact requirescareful alignment and consistent pressure. The results across an entiredisplay are not good and displays created with such techniquesfrequently contain many dead pixels and high voltage OLEDs due to thepoor quality of the electrical path between the contact and the OLED.

SUMMARY

Aspects of the present disclosure provide an organic light emittingdiode (“OLED”) which is prepared by depositing a first terminal on afirst substrate, and a second terminal on a second substrate. Aplurality of layers forming the inner region of the OLED between thefirst terminal and the second terminal is divided into a first portionand a second terminal. The first portion of the plurality of layers isthen deposited on the first terminal and the second portion of theplurality of layers is deposited on the second terminal. The firstsubstrate and the second substrate are then aligned and the firstportion and the second portion are joined together.

The first portion of the plurality of layers can include a first part ofa common layer, and the second portion of the plurality of layers caninclude a second part of the common layer. The first and second parts ofthe common layer can each be the last deposited of the first and secondportions of the plurality of layers, respectively. The first portion andthe second portion can be aligned such that the exposed surfaces of thetwo parts of the common layer meet at an intralayer interface. The twoparts of the common layer are annealed together to form a unified commonlayer, and thereby join together the first and second portions of theOLED.

The foregoing and additional aspects and embodiments of the presentinvention will be apparent to those of ordinary skill in the art in viewof the detailed description of various embodiments and/or aspects, whichis made with reference to the drawings, a brief description of which isprovided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings.

FIG. 1A illustrates a symbolic plan of a first portion of an organiclight emitting diode.

FIG. 1B illustrates a symbolic plan of a second portion of an organiclight emitting diode.

FIG. 2 is a flowchart of a process for forming an organic light emittingdiode from two portions.

FIG. 3A illustrates a symbolic plan of a first and second portion of theorganic light emitting diode while the two portions are aligned to bejoined together.

FIG. 3B illustrates a symbolic plan of the organic light emitting diodeshown in FIG. 3A following an annealing process to infuse the commonlayer together.

FIG. 4A is a flowchart of a process for forming an organic lightemitting diode by annealing two parts of a common layer.

FIG. 4B illustrates a flowchart of a process similar to that shown inthe flowchart in FIG. 4A, but further illustrating several aspects ofthe process performed in parallel.

FIG. 5A is a vertical section of an assembled first portion of anorganic light emitting diode formed on an encapsulation substrate.

FIG. 5B is a vertical section of an assembled second portion of anorganic light emitting diode formed on a TFT substrate and configured tojoin the first portion illustrated in FIG. 5A.

FIG. 5C is a vertical section of an organic light emitting diode formedby annealing a first part and a second part of a common layer of thefirst and second portions shown in FIGS. 5A and 5B.

FIG. 6A is a vertical section of a first portion of an organic lightemitting diode similar to that shown in FIG. 5A and incorporatingspacers.

FIG. 6B is a vertical section of a second portion of an organic lightemitting diode similar to that shown in FIG. 5B and incorporatingspacers.

FIG. 6C is a vertical section of an organic light emitting diode formedby annealing a first part and a second part of a common layer of thefirst and second portions shown in FIGS. 6A and 6B.

FIG. 7A is a vertical section of a first portion of an organic lightemitting diode similar to that shown in FIG. 6A and incorporating banks

FIG. 7B is a vertical section of a second portion of an organic lightemitting diode similar to that shown in FIG. 6B and configured to bejoined to the first portion illustrated in FIG. 7A.

FIG. 7C is a vertical section of an organic light emitting diode formedby annealing a first part and a second part of a common layer of thefirst and second portions shown in FIGS. 7A and 7B.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. Itshould be understood, however, that the invention is not intended to belimited to the particular forms disclosed. Rather, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1A illustrates a symbolic plan of a first portion 2 of an organiclight emitting diode. The first portion 2 is deposited on a firstsubstrate 10 in sequentially developed layers. The first OLED terminal12 is formed on the first substrate 10. For example, in animplementation where the first substrate 10 is a transparent substratesuch as an encapsulation glass, the first OLED terminal can be an anodeterminal formed of a transparent conductive material such as indium tinoxide (“ITO”). On the first OLED terminal 12, 0 to N layers 14 of theOLED are deposited. The 0 to N layers 14 can include, for example, ahole injection layer, a hole transfer layer, an emission layer, anelectron transfer layer, an electron injection layer, and/or aplanarization layer. The 0 to N layers 14 can also include no layers.Appropriately doped semiconductive, organic, and/or inorganic materialscan be selected as appropriate for particular implementations of theOLED based on desired emission performance characteristics. Furthermore,one or more of the plurality of layers can be omitted and/or combinedwith other layers. The first portion 2 can optionally terminate with afirst part 16 a of a common layer.

FIG. 1B illustrates a symbolic plan of a second portion 4 of an organiclight emitting diode. The second portion 4 is formed similarly to thefirst portion 2. The first portion 4 is deposited on a second substrate22. For example, the second substrate 22 can be a glass planarizationsubstrate over a terminal of a TFT. The second portion 4 includes asecond OLED terminal 20. The second OLED terminal 20 can be a cathodeterminal formed of a reflective metallic material having a high workfunction. On the second OLED terminal 20, 0 to M layers 18 of the OLEDare deposited. The 0 to M layers 18 can include, for example, any of theplurality of layers recited for the 0 to N layers 14 in connection withFIG. 1A. The 0 to M layers 18 can also include no layers, in which caseall of the plurality of layers of the OLED, other than the second OLEDterminal 20, are developed on the first substrate 10. The second portion4 can optionally terminate with a second part 16 b of the common layer.In implementations including the first part 16 a and the second part 16b, the parts 16 a, 16 b jointly comprise the common layer of the OLED.The common layer can be any of the plurality of layers recited inconnection with the 0 to N layer 14 or the 0 to M layer 18. For example,the common layer can be the electron transfer layer. In implementationsincorporating the first part 16 a and the second part 16 b, the twoparts can each be substantially equal to half of the common layer, orcan be another complementary matched set of portions of the common layersuch that the two parts 16 a, 16 b jointly form the common layer whenthe two parts 16 a, 16 b are joined together.

FIG. 2 illustrates a flowchart 30 of a process for forming an organiclight emitting diode from two portions for use in a display. FIG. 2 willbe described in connection with the first portion 2 and the secondportion 4 illustrated in FIGS. 1A and 1B. The first portion 2 of theOLED is formed on a first substrate 10 of the display (32). The secondportion 4 of the OLED is formed on a second substrate 22 of the display(34). To complete the preparation of the OLED, the first portion 2 andthe second portion 4 are joined together (36).

FIG. 3A illustrates a symbolic plan of the first portion 2 and thesecond portion 4 of the organic light emitting diode while the twoportions are aligned to be joined together. In the implementation shownin FIGS. 3A and 3B, the first portion 2 and the second portion 4 eachinclude a respective first part 16 a and second part 16 b of the commonlayer, which is joined together by an annealing process (FIG. 3B) toinfuse (“join”) the first portion 2 to the second portion 4. As shown inFIG. 3A, the first portion 2 is positioned such that the first part 16 aabuts the second part 16 b at an interface.

FIG. 3B illustrates a symbolic plan of the organic light emitting diode6 shown in FIG. 3A following an annealing process to infuse the commonlayer 16 together. The first part 16 a and the second part 16 b aresubjected to annealing, which can include thermal, pressure, or optical(e.g., laser) annealing. The resulting common layer 16 is a unitarylayer. By terminating the first portion 2 and the second portion 4 neara mid-point of the common layer 16, such that the annealing processinfuses an intralayer interface of the common layer, the annealingprocess avoids any interlayer interfaces. Interlayer interfaces can bemore critical to the performance of the OLED than annealed intralayerinterfaces, and therefore interlayer interfaces (e.g., the interfacesbetween the plurality of layers in the 0 to N layers 14 and/or the 0 toM layers 18) are advantageously formed by the layered deposition processrather than by an annealing process.

FIG. 4A is a flowchart 40 of a process for forming an organic lightemitting diode for use in a display by annealing two parts of a commonlayer. A first terminal (e.g., the first terminal 12) is formed on atransparent substrate (e.g., a transparent encapsulation glass) of adisplay (42). 0 to N layers (e.g., the 0 to N layers 14) of the OLED aredeveloped on the first terminal (44). The 0 to N layers are sequentiallydeposited on the first terminal. The 0 to N layers can include, forexample, a hole injection layer, a hole transfer layer, an emissionlayer, an electron transfer layer, an electron injection layer, and/or aplanarization layer. In addition, one or more of the layers can beomitted and/or combined with other layers. In an example, the 0 to Nlayers can include a hole injection and transfer layer, formed on thefirst terminal, and an emission layer, formed on the hole injection andtransfer layer. A first part of a common layer (e.g., the electrontransfer layer) is then developed on the 0 to N layers (46).

FIG. 4B is a flowchart 40′ of a process similar to that shown in theflowchart in FIG. 4A, but further illustrating several aspects of theprocess performed in parallel. In particular, FIG. 4B illustrates thatforming the first portion (e.g., the first portion 2) of the OLED on thetransparent substrate (42, 44, 46) can be carried out in parallel withforming the second portion (e.g., the second portion 4) on the substrateof a drive TFT (48, 50, 52). Parallel operations can advantageouslyallow for faster production times. Following the parallel operations,the two portions are joined together by annealing the two parts of thecommon layer together (54). While the flowcharts 40 and 40′ are providedto illustrate two exemplary implementations of the present disclosure,the present disclosure is not limited to implementations where thevarious stages to develop the OLED are performed strictly serially or inparallel. Implementations of the present disclosure can be realizedincorporating a combination of serial ordering and parallel ordering.

Next a schematic of a particular example of an OLED developed accordingto an example implementation of the present disclosure is described. Theviews shown in FIGS. 5A through 7C are generally cross sectional viewsof the first and second portions of the OLED, and the OLED after it hasbeen infused (“joined”). The views schematically illustrate an exampleof the plurality of layers of the OLED, but the schematic views are forillustrative purposes and are not drawn to scale (e.g., the schematicillustrations are not intended to convey the relative thicknesses of theplurality of layers of the OLED).

FIG. 5A is a vertical section of a first portion 102 of an organic lightemitting diode formed on an encapsulation substrate 60. Theencapsulation substrate 60 has an enclosed side 62 and an exposed side64. An anode terminal 66 is formed on the enclosed side 62 of theencapsulation substrate 60. The encapsulation substrate 60 and the anodeterminal are each desirably substantially visually transparent to allowlight from the OLED to be emitted through the exposed side 64. The anodeterminal 66 can be formed from indium tin oxide (“ITO”) or a comparableconductive visually transparent material. The anode terminal 66 can beformed on the encapsulation substrate 60 by a deposition process todevelop a layer of ITO (or comparable material) on the encapsulationsubstrate 60. A hole transfer and injection layer 68 is then developed(e.g., “deposited”) on the anode terminal 66. The hole transfer andinjection layer 68 can be developed on the anode terminal 66 by adeposition process or a similar technique. An emission layer 70 is thendeveloped on the hole transfer and injection layer 68. A first part 72 aof an electron transfer layer is developed on the emission layer 70. Thefirst part 72 a of the electron transfer layer has an exposed firstsurface 74. The first part 72 a of the electron transfer layer isapproximately half of the thickness of the full electron transfer layer(72 in FIG. 5C). The development of the first portion 102 is halted withthe exposed first surface 74.

FIG. 5B is a vertical section of a second portion 104 of the organiclight emitting diode formed on a TFT substrate and configured to jointhe first portion 102 illustrated in FIG. 5A. A planarization substrate82 is developed on a drain terminal 84 of the TFT. The planarizationsubstrate 82 is formed with an aperture 85 such that at least a portionof the drain terminal 84 remains exposed through the planarizationsubstrate 82. A cathode terminal 80 is then developed (e.g.,“deposited”) on the aperture 85 such that the cathode terminal 80 issecurely electrically coupled to the drain terminal 84 of the TFT. Anelectron injection layer 78 is then developed on the cathode terminal80. The second part 72 b of the electron transfer layer is thendeveloped on the electron injection layer 78. The second part 72 b ofthe electron transfer layer can be approximately half of the electrontransfer layer such that the first part 72 a and the second part 72 btogether form the full electron transfer layer. The second part 72 bincludes an exposed second surface 76. The development of the secondportion 104 is halted with the exposed second surface 76 of the secondpart 72 b.

The development of the plurality of layers 66, 68, 70, 72 a, 72 b, 78,80, 82 of the first portion 102 and the second portion 104 can each beformed by a deposition process or similar technique for forming thinfilms of material.

FIG. 5C is a vertical section of an organic light emitting diode 106formed by annealing the first part 72 a and the second part 72 b of theelectron transfer layer shown in FIGS. 5A and 5B. The first portion 102is positioned such that the exposed first surface 74 of the first part72 a of the electron transfer layer abuts the exposed second surface 76of the second part 72 b of the electron transfer layer. The interfacebetween the exposed surfaces 74, 76 is thus an intralayer interface, andthe two parts 72 a, 72 b can be infused (“joined”) by annealing the twoparts 72 a, 72 b together to form the unitary electron transfer layer72. The annealing can be accomplished by a thermal annealing process at,for example, 200 to 300 degrees Celsius.

An exemplary operation of the OLED 106 illustrated schematically in FIG.5C is described next. In operation, the TFT begins to drive a current toflow generally toward the drain terminal 84, such that the cathodeterminal 80 acquires a negative voltage with respect to the anodeterminal 66. Once the voltage difference between the cathode terminal 80and the anode terminal 66 is sufficient to exceed an operating voltage(i.e., “on voltage”) of the OLED, electrons injected in the electroninjection layer 78 from the cathode terminal 80. The injected electronsare urged generally away from the cathode terminal 80 toward theemission layer 70, which can be considered a recombination layer. At thesame time, positively charged holes are injected from the anode terminal66 and transferred through the hole injection and transfer layer 68. Theholes are urged generally away from the anode terminal 66 toward theemission layer 70.

In the emission layer, the electrons generally occupy the lowestunoccupied molecular orbital level (LUMO) in the emission layer 70 untilrecombining with a hole. The recombined electrons radiatively decay tothe highest occupied molecular orbital level (HOMO) in the emissionlayer 70, and light is emitted according to the accompanying change inenergy. The light emitted from the emission layer 70 passes through theencapsulation substrate 60 to emerge from the exposed side 64 of theencapsulation surface. Light that is initially directed away from theencapsulation surface 60 (e.g., toward the cathode terminal 80) isdesirably reflected by the cathode terminal 80 to be emitted through theencapsulation surface 60. The cathode terminal 60 is advantageouslyformed from a reflective substance, such as a metallic material. Thecathode terminal 80 is also advantageously selected to have a workfunction suitable to injection electrons having an energy sufficient tooccupy the LUMO in the emission layer 70. Thus, the materialcharacteristics of the emission layer 70 (e.g., HOMO and LUMO) caninfluence the selection of the cathode terminal 80, and also the anodeterminal 66.

FIG. 6A illustrates a first portion 102′ of an organic light emittingdiode similar to that shown in FIG. 5A, but incorporating spacers 112,114. In the cross-sectional view of FIG. 6A, the spacers 112, 114 areplaced on the opposing sides of the first portion 102′. The spacers 112,114 are placed on the anode terminal 66 to avoid interrupting signalscarried on the anode terminal 66, however, the spacers 112, 114 can beplaced on other layers such as, for example, the hole injection andtransfer layer 68. The spacers 112, 114 can completely surround thepixel area of the OLED and can include a plurality of columns and/orcylinders arranged horizontally and/or vertically with respect to theplane of the display. The spacers 112, 114 can be composed of materialsincluding, for example, a nitrides and/or oxides. The spacers 112, 114can advantageously provide a physical separation between layers ofadjacent OLEDs developed on the encapsulation substrate 60. As describedin connection with FIG. 6C, the spacers 112, 114 can also regulate thepressure applied to the OLED 106′ to prevent the OLED 106′ from beingcompacted (“crushed”) when the first portion 102′ and the second portion104′ are joined together.

During manufacturing, the spacers 112, 114 can also assist in thealignment of a shadow mask which covers pixels not receiving depositedsemiconductor layers. For example, when a patterned red, green, and blueconfiguration of pixels is being developed on the encapsulationsubstrate, the shadow mask can be placed over the display panel toprovide small holes through which layers for particular colors can bedeposited on the corresponding the pixel areas. By providing the spacers112, 114, the shadow mask can rest on the spacers and avoid warping orstretching of the shadow mask when positioning it over the displaypanel.

FIG. 6B illustrates a second portion 104′ of an organic light emittingdiode similar to that shown in FIG. 5B, but incorporating spacers 114,116. Similar to the description of the spacers 112, 114 provided inconnection with FIG. 6A, the spacers 114, 116 are placed (“positioned”)on the planarization substrate 82. The spacers 114, 116 areadvantageously positioned to be aligned with the spacers 112, 114 of thefirst portion 102′ such that the spacers 114, 116 abut correspondingones of the spacers 112, 114 when the first portion 102′ is joined tothe second portion 104′.

FIG. 6C illustrates an organic light emitting diode formed by annealinga first part and a second part of a common layer of the first and secondportions shown in FIGS. 6A and 6B. The OLED 106′ is similar to the OLED106 shown in FIG. 5C, except that the OLED 106′ includes the spacers. Asshown in FIG. 6C the respective spacers of the first portion 102′ andthe second portion 104′ abut one another in the assembled OLED 106′ toprotect the deposited layers of the OLED 106′ (e.g., the layers 70, 72,78, 80) from being damaged due to compression during the joining of thetwo portions. Properly aligned at assembly, the spacer 114 of the firstportion 102′ abuts the spacer 116 of the second portion 104′ and thespacer 112 of the first portion 102′ abuts the spacer 118 of the secondportion 104′.

FIG. 7A illustrates a first portion 102″ of an organic light emittingdiode similar to that shown in FIG. 6A and incorporating banks 122, 124.The banks 122, 124 are placed (“positioned”) on the anode terminal 66 tosurround the hole injection and transfer layer 68. As shown in FIG. 7A,the bank structure provided by the banks 122, 124 prevent the first part72 a of the electron transfer layer from abutting the hole injection andtransfer layer 68. The bank structure thus contributes to theperformance of the OLED 106″ by ensuring that the recombination eventsoccur substantially within the emission layer 70 rather than in theregions where the electron transfer layer 72 directly abuts the holeinjection and transfer layer 68. For example, FIGS. 5A and 6A provideexamples where a sub-region of the electron transfer layer 72 directlyabuts a sub-region of the hole injection and transfer layer 68, thusproviding a path for electrons to recombine with holes outside of theemission layer 70.

FIG. 7B illustrates a second portion 104′ of an organic light emittingdiode similar to that shown in FIG. 6B and configured to be joined tothe first portion illustrated in FIG. 7A. FIG. 7C illustrates an organiclight emitting diode 106″ formed by annealing a first part and a secondpart of a common layer of the first and second portions shown in FIGS.7A and 7B. As shown in FIG. 7C, the assembled OLED 106″ includes boththe spacers structure described in connection with FIGS. 6A through 6C,and the bank structure described in connection with FIG. 7A.

Aspects of the present disclosure provide for annealing two parts of acommon layer that meet at an intralayer interface to join together firstand second portions of an OLED. For example, the common layer can be anelectron transfer layer. In implementations where the design parametersof the OLED provide that the electron transfer layer is the thickestlayer of the OLED, utilizing the electron transfer layer as the commonlayer can be advantageous because the two parts of the common layerseparately deposited on the first portion and the second portion arethicker than if another layer is utilized as the common layer.

Aspects of the present disclosure can also be applied to OLEDs in amulti-stacked structure. In a multi-stack OLED, a first portion of themulti-stack OLED is developed on a first substrate, and a second portionof the multi-stack OLED is developed on a second substrate. The twoportions are then joined together to form the multi-stack OLED.

Aspects of the present disclosure also apply to color displays.Individual OLEDs can be formed (“manufactured”) according to the presentdisclosure with a color filter introduced between the emission layer 70and the exposed side 64 of the encapsulation substrate 60. Inimplementations where the OLED is configured to emit, for example, whitelight, color filters can be inserted to provide for emission of basecolors of a color display such as, for example, red, green, and bluefilters. Additionally or alternatively, the OLED can be configured (suchas by choice of the compositions and/or thicknesses of the plurality oflayers in the OLED) to emit particular colors of light, and a pattern ofdifferent colors can be repeated across a display to form a colordisplay having, for example, red, green, and blue color components.

Aspects of the present disclosure provide a method of manufacturing anOLED by separately forming opposing terminals of the OLED on twoseparate substrates, developing a plurality of layers of the OLED on oneor both of the two terminals, and joining together the two portions.OLEDs manufactured by this process offer advantages over existing OLEDs,because both terminals are deposited on the respective substrates.Electrical connections to each terminal of the OLED, such as anelectrical connection to a terminal of a driving transistor, do not relyon separate contacts that must be carefully aligned and which canrequire pressure to maintain efficient charge transfer. In particular,the cathode terminal can be directly deposited on the drain terminal ofan n-type thin film transistor acting as a drive transistor. Such aconfiguration allows the drive transistor to drive current through theformed OLED while the gate-source voltage of the drive transistor(“Vgs”) is unaffected by the operating voltage of the OLED. Inparticular, a shift in the operation voltage of the OLED (“V_(OLED)”)over the lifetime of the OLED does not impact the voltage Vgs appliedacross the drive transistor. OLEDs formed according to aspects of thepresent disclosure provide a reverse OLED configuration such that thecathode of the OLED can be securely coupled (e.g., by a deposition,evaporation, or similar process) to a drain terminal of an n-type drivetransistor. Aspects of the present disclosure can also be applied toforming an OLED with an anode terminal deposited on a source terminal ofa p-type drive transistor.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationscan be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

1-12. (canceled)
 13. A method of manufacturing an organic light emittingdiode having a first terminal, a second terminal, and a plurality oflayers between the first terminal and the second terminal, the methodcomprising: forming, on a first substrate, the first terminal of theorganic light emitting diode; forming, on a second substrate, the secondterminal of the organic light emitting diode; developing a first portionof the plurality of layers on the first terminal; developing a secondportion of the plurality of layers on the second terminal; and joiningthe first portion of the plurality of layers to the second portion ofthe plurality of layers such that the plurality of layers is situated inbetween the first terminal and the second terminal.
 14. The method ofclaim 13, wherein the plurality of layers includes a common layer havinga first part included in the first portion of the plurality of layers,the common layer having a second part included in the second portion ofthe plurality of layers, and wherein: the developing the first portionof the plurality of layers includes depositing the first part of thecommon layer, the developing the second portion of the plurality oflayers includes depositing the second part of the common layer, and thejoining is carried out by annealing the first part and the second partof the common layer.
 15. The method of claim 14, wherein the commonlayer is an electron transfer layer.
 16. The method of claim 13, whereinthe plurality of layers includes: an emission layer, a hole transferlayer, or an electron transfer layer, and wherein the first portion andthe second portion of the plurality of layers each include at least onelayer of the plurality of layers.
 17. The method of claim 13, furthercomprising: prior to the joining, placing a first spacer on the firstportion of the plurality of layers and a second spacer on the secondportion of the plurality of layers, and wherein during the joining, thefirst spacer abuts the second spacer so as to prevent the plurality oflayers from being compressed.
 18. The method of claim 13, wherein thedeveloping the first portion of the plurality of layers or thedeveloping the second portion of the plurality of layers includesplacing a bank at a periphery of a hole transfer layer so as to preventthe hole transfer layer from abutting an electron transfer layer. 19-21.(canceled)